outline th key characteristics that destinguish the three domains Include examples of organisms in each domain

Answer 1

The three-domain system of Carl Woese, introduced in 1990, with top-level groupings of Archaea, Bacteria, and Eukaryota domains.

Domain Archaea : Life's Extremists...! Archaea are found in the harshest environments on Earth, and are the oldest known organisms on Earth, appearing in the fossil record over 3.6 BILLION years ago (3,600,000,000 years ago!)

1. Methanogens: the“methane-makers”
Use only CO2, H and N to produce energy to live, and as a result give off methane gas. Live in swamps, marshes, gut of cattle, termites, etc. Methanococcus jannaschii, isolated from the deep sea Alvin probe, was the first Archaean whose genome was sequenced. Methanogens are decomposers; and can be used in sewage treatment. Methanogens may someday be used to produce methane as fuel!

2. Extreme Halophiles: the “salt lovers”
Require an environment as salty or even10x saltier than ocean water. Some prefer up to 30% salt concentrations! These bacteria live in the Dead Sea, the Great Salt Lake, salt evaporation ponds.

3. Extreme Thermophiles: “heat / cold lovers”
Prefer temperatures above 60°C (up to 110°C for hyperthermophiles!) or near or below freezing. (Some thermophiles will die at roon temperature).
Thermophiles ive in hot sulfur springs, Yellowstone Park, deep sea hydrothermal vents “black smokers”, geothermal power plants. Also live in ocean waters around Antarctica, under the polar ice caps, etc. Thermus aquaticus and Pyrococcus furiosis and two species

Domain Bacteria: Domain Bacteria (or Eubacteria) is familiar to most people when associated with human or animal disease. However, most bacterial species do not (and cannot) cause disease. Most species even play beneficial roles for humans by producing antibiotics and food. The soil, and in fact all ecosystems on earth, teems with free-living bacteria that perform many essential functions in the biosphere, e.g. nitrogen fixation, decomposition of organic material, etc.

1. Cyanobacteria: Photosynthetic ‘blue-green’ bacteria = produce O2 gas. Photosynthetic bacteria first appeared in the fossil record 3.2 billion years ago, and completely changed Earth's environment from anaerobic (no free oxygen) to aerobic (containing oxygen gas) - these bacteria made the O2 rich atmosphere in which we live!!! These bacteria are very closely related to eukaryotic chloroplasts (more on this later).

2. Eubacteria: The "true bacteria". Examples: Enteric bacteria like E. coli, Salmonella typhus, Legionella, Heliobacter pylorii (cause of many ulcers), Neisseria gonorrhea (cause of gonorrhea), Nitrogen-fixing bacteria that are able to convert nitrogen gas into ammonia. Clostridium (tetanus, botulism). Bacteria within this division - proteobacteria - are very closely related to eukaryotic mitochondria (more on this later) and often move by whip-like flagella

Domain Eukarya: 4 Kingdoms of Eukaryotes!

1. Protista – Single celled eukaryotes – Euglena, Amoeba, Paramecium etc. These single celled organisms with a nucleus are first seen in the fossil record 1.5 billion years ago.

Protists can be found on land, in water, or living inside other organisms. Some protists are photosynthetic, like "phytoplankton", and produce more oxygen than all land plants put together. Other protists are parasites or predators. The protozoan Trypanosoma brucei causes African Sleeping Sickness. This parasite it transmitted to man by the bite of the tsetse fly. Another protozoan, Entameba histolytica is a parasite of the stomach which kills cells and drinks blood (but do not actually kill their host). The protozoan Plasmodium vivax causes malaria, carried by female mosquitos. Many protozoans move by means of pseudopodia

2. Fungi – Mushrooms, bread molds, water molds, yeasts ,etc.

The Kingdom Fungi includes some of the most important organisms on Earth. By breaking down dead organic material, they cycle nutrients through ecosystems. Other fungi provide drugs such as penicillin and other antibiotics, foods like mushrooms, truffles and morels, and the bubbles in bread, champagne, and beer.

Fungi also cause plant and animal diseases: in humans, ringworm, athlete's foot, and several more serious diseases are caused by fungi. Plant diseases caused by fungi include rusts, smuts, and leaf, root, and stem rots, and may cause severe damage to crops. However, a number of fungi, in particular the yeasts, are important "model organisms" for studying problems in genetics and molecular biology

3. Plantae – Flowering plants, gymnosperms (conifers), ferns, mosses, etc

Kingdom Plantae includes all land plants - an amazing range of diverse forms with more than 250,000 species. Plants first appeared on Earth in the Ordovician period approximately 460 million years ago (mya), as bryophyes (mosses), with the first ferns appearing 410 mya, the first seed plants (gymnosperms) appearing 360 mya, and finally, the first flowering plants (angiosperms) appearing just 130 mya. The most striking, and important, feature of plants is their green color, the result of a pigment called chlorophyll. Plants use chlorophyll to capture light energy, which fuels the manufacture of food—sugar, starch, and other carbohydrates

4. Animalia – There is so much to say about this Kingdom

http://cas.bellarmine.edu/tietjen/RootWeb/three_domains_theory.htm